1. Field of the Invention
This invention relates to rotary compressors used for an apparatus, e.g., air conditioners, refrigerators, etc., for compressing a gaseous fluid.
2. Description of the Prior Art
In general, a rotary compressor is used with a refrigerating circuit for compressing a gaseous fluid. FIGS. 1 and 2 show a conventional rotary compressor. A rotary compressor 11 typically includes a cylinder 13, a rotation shaft 15 and a blade 17. A compressing chamber 19 is defined by the inner surface of cylinder 13. A pair of bearing (not shown) are respectively arranged to the opposite ends of cylinder 13 to establish compressing chamber 19. Rotation shaft 15 penetrates compressing chamber 19 and is rotatably supported by the pair of bearings. Compressing chamber 19 is provided with a roller 21. A penetrating hole is formed at the center of roller 21. Rotation shaft 15 extends through the penetrating hole. The outer surface of an eccentric portion 15a of rotation shaft 15 loosely contacts the inner surface of roller 21. An eccentric amount of eccentric portion 15a from the center of rotation shaft 15 is indicated by a distance E. Therefore, roller 21 eccentrically rotates along the inner surface of cylinder 13 in response to the rotation of shaft 15. A blade guide groove 23 extends from the inner surface of cylinder 13 toward the outer surface of cylinder 13 in the radial direction of cylinder 13. Blade 17 which has a length l.sub.1 is disposed in blade guide groove 23, and is forcibly urged toward roller 21 by a spring 25 shown in FIG. 3 to reciprocate along balde guide groove 23 in response to the eccentric rotation of roller 21. As shown in FIG. 3, one end of spring 25 is supported by a channel formed at the one side of blade 17. The other end of spring 25 is supported by the inner surface of a compressor housing (not shown) when compressor is assembled into the housing. Therefore, as described above, the other side of blade 17 is always in contact with the outer surface of roller 21. Blade 17 partitions compressing chamber 19 into a high pressure cell and a low pressure cell for compressing a gaseous fluid, e.g., refrigerant, fed to compressing chamber through an intake port 27 in response to the eccentric rotation of shaft 15.
In the above described conventional rotary compressor 11, however, if the stroke of blade 17 is longer than the length of blade 17, a portion of blade 17 which is supported by balde guide groove 23 becomes small when blade 17 comes to a lower dead point, as shown in FIG. 1. When rotation shaft 15 rotates in the direction indicated by arrow A, blade 17 always is subject to the difference in pressure between the intake side cell (low pressure side) and the discharge side (high pressure side) during the compressing operation. Therefore, a moving resistance between blade 17 and blade guide groove 23 increases when blade 17 approaches the lower dead point. In other words, the pressure acting on the unit area of the inner side surface of blade guide groove 23 by blade 17 increases, as blade 17 comes to the lower dead point. As a result, the power consumption of compressor 11 increases, and the compression ability of compressor 11 is reversely affected.
To avoid disadvantages described above, inventors of the present invention have attempted to increase the length of blade 17 in a reciprocating direction. The length of blade guide groove 23 also was increased. With this construction, the contacting area between blade 17 and blade guide groove 23 can be increased in the reciprocating direction when blade 17 is at the lower dead point. However, the stiffness of cylinder 13 decreases because of the increase of the length of blade guide groove 23. The thickness of cylinder 13 should be increased so that the stiffness of cylinder 13 is increased, resulting in a large external shape of compressor 11 as well as the increase in cost.